Complex muscle vibration patterns to induce gait-like lower-limb movements: proof of concept

Development and deployment of cyclical focal muscle vibration system to improve walking performance in multiple sclerosis

Vibration, a potent mechanical stimulus for activating muscle spindle primary afferents, may improve gait performance in persons with multiple sclerosis (MS), but has yet to be developed and deployed for multiple leg muscles with application during walking training. This study explored the development of a cyclic focal muscle vibration (FMV) system, and the deployment feasibility to correct MS walking swing phase deficits in order to determine whether this intervention warrants comprehensive study. The system was deployed during twelve, two-hour sessions of walking with cyclic FMV over six weeks. Participants served as their own control. Blood pressure, heart rate, walking speed, kinematics (peak hip, knee and ankle angles during swing), toe clearance, and step length were measured before and after deployment with blood pressure and heart rate monitored during deployment. During system deployment, there were no untoward sensations and physiological changes in blood pressure and heart rate, and volitional improvements were found in walking speed, improved swing phase kinematics, toe clearance and step length. This FMV training system was developed and deployed to improve joint flexion during walking in those with MS, and it demonstrated feasibility and benefits. Further study will determine the most effective vibration frequency and dose, carryover effects, and those most likely to benefit from this intervention.

Simultaneous Control of Tonic Vibration Reflex and Kinesthetic Illusion for Elbow Joint Motion Toward Novel Robotic Rehabilitation

Robotic rehabilitation is one of the most promising applications of robotic technologies. It is known that patients' active participation in rehabilitation is important for their recovery. On the other hand, mechanical vibration stimulation to muscles induces tonic vibration reflex (TVR) and kinesthetic illusion (KI) in the joint motion. In this paper, the possibility of a novel robotic rehabilitation method, in which the TVR is applied to an agonist muscle to enhance the intended motion of patients and the KI is simultaneously applied to an antagonist muscle to enhance the kinesthetic movement sensation of the generating intended motion by changing the frequency of vibration stimulation, is investigated. As the first step toward novel robotic rehabilitation, the proposed method is evaluated in elbow joint motion. The experimental results show the possibility of the proposed novel rehabilitation method.Clinical Relevance- This study shows the possibility of novel robotic rehabilitation.

Perception of gait motion during multiple lower-limb vibrations in young healthy individuals: a pilot study

In virtual reality (VR), immersion can be created through synchronous visuomotor stimulations and enhanced by adding auditory or kinesthetic stimulations. Multiple patterned vibrations applied at the lower limbs might be a way to induce kinesthetic perception of gait motion that could be combined with VR stimulations to add the perception of self-motion. However, gait motion perception using multiple vibrations has not yet been evaluated. The objective of the study was to quantify the perception of gait motion while applying multiple, patterned vibrations to the lower limbs in healthy individuals. Twenty young healthy participants (25.1 ± 4.4 years) experienced multiple vibrations in 1-min trials. Stimulation consisted of a vibration pattern based on the sequence of muscle lengthening during a 2-s gait cycle. Stimulation was applied on participants in a standing position, under 11 experimental conditions controlling visual information (eyes open/closed), vibration frequency (40-80 Hz), and number and location of the joints stimulated (hips, knees, ankles isolated or combined two by two). Perception of gait motion was quantified for each condition using a 10-point visual analog scale (VAS, 0: "no perception", 10: "Perception of gait movements"). All participants except one achieved a score higher than 5/10 in at least one condition. Great variability was found for perception of gait motion within participants and conditions (VAS ranging from 0 to 9.6/10). Differences were found between conditions (p < 0.01), with higher mean and median scores in conditions that included knee vibration. Inducing gait motion perception is possible using multiple vibrations in healthy individuals. Stimulation of the knees seems to positively influence perception of gait motion.

Accuracy and precision of a wrist movement when vibrotactile prompts inform movement speed

Purpose: This study investigated the effect of movement speed on task accuracy and precision when participants were provided temporally oriented vibrotactile prompts. Materials and methods: Participants recreated a simple wrist flexion/extension movement at fast and slow speeds based on target patterns conveyed via vibrating motors affixed to the forearm. Each participant was given five performance-blinded trials to complete the task at each speed. Movement accuracy (root mean square error) and precision (standard deviation) were calculated for each trial in both the spatial and temporal domains. Results: 28 participants completed the study. Results showed temporal accuracy and precision improved with movement speed (both: fast > slow, p < 0.01), while all measures improved across trials (temporal accuracy and precision: trial 1 < all other trials, p < 0.05; spatial accuracy: trial 1 and 2 < all other trials, p < 0.05; spatial precision: trial 1 < all other trials, p < 0.05). Conclusions: Overall, temporal and spatial results indicate participants quickly recreated and maintained the desired pattern regardless of speed. Additionally, movement speed seems to influence movement accuracy and precision, particularly within the temporal domain. These results highlight the potential of vibrotactile prompts in rehabilitation paradigms aimed at motor re-education.

A new method to elicit and measure movement illusions in stroke by means of muscle tendon vibration: the Standardized Kinesthetic Illusion Procedure (SKIP)

Purpose: Muscle tendon vibration (MTV) strongly activates muscle spindles and can evoke kinaesthetic illusions. Although potentially relevant for sensorimotor rehabilitation in stroke, MTV is scarcely used in clinical practice, likely because of the absence of standardised procedures to elicit and characterise movement illusions. This work developed and validated a Standardised Kinaesthetic Illusion Procedure (SKIP) to favour the use of MTV-induced illusions in clinical settings.Materials and methods: SKIP scores were obtained in 15 individuals with chronic stroke and 18 age- and gender-matched healthy counterparts. A further 13 healthy subjects were tested to provide more data with the general population. MTV was applied over the Achilles tendon and SKIP scoring system characterised the clearness and direction of the illusions of ankle dorsiflexion movements.Results: All healthy and stroke participants perceived movement illusions. SKIP scores on the paretic side were significantly lower compared to the non paretic and healthy. Illusions were less clear and sometimes in unexpected directions with the impaired ankle, but still possible to elicit in the presence of sensorimotor deficits.Conclusions: SKIP represents an ancillary and potentially useful clinical method to elicit and characterise illusions of movements induced by MTV. SKIP could be relevant to further assess the processing of proprioceptive afferents in stroke and their potential impact on motor control and recovery. It may be used to guide therapy and improve sensorimotor recovery. Future work is needed to investigate the metrological properties of our method (reliability, responsiveness, etc.), and also the neurophysiological underpinnings of MTV-induced illusions.

The effects of muscle vibration on gait control: a review

Background: The purpose of the review is to summarize the literature surrounding the use of muscle vibration as it relates to modifying human gait. Methods: After a brief introduction concerning historical uses and early research identifying the effect of vibration on muscle activation, we reviewed 32 articles that used muscle vibration during walking. The review is structured to address the literature within four broad categories: the effect of vibration to 'trigger' gait-like lower limb motions, the effect of vibration on gait control of healthy individuals and individuals with clinical conditions in which gait disorders are a prominent feature, and the effect of vibration training protocols on gait. Results: The acute effects of vibration during gait involving healthy participants is varied. Some authors reported differences in segmental kinematic and spatiotemporal measures while other authors reported no differences in these outcome measures. The literature involving participants with clinical conditions revealed that vibration consistently had a significant impact on gait, suggesting vibration may be an effective rehabilitation tool. All of the studies that used vibration therapy over time reported significant improvement in gait performance. Conclusions: This review highlights the difficulties in drawing definitive conclusions as to the impact of vibration on gait control, partly because of differences in walking protocols, site of vibration application, and outcome measures used across different investigative teams. It is suggested that the development of common investigative methodologies and outcome measures would accelerate the identification of techniques that may provide optimal rehabilitation protocols for individuals experiencing disordered gait control.

Gait-like vibration training improves gait abilities: a case report of a 62-year-old person with a chronic incomplete spinal cord injury

The purpose of this single-subject case study was to quantify the effect of gait-like vibration training on gait abilities after an incomplete spinal cord injury (SCI). A 62-year-old male with a chronic American Spinal Injury Association Impairment Scale D SCI at T11 completed nine sessions of gait-like vibration training in a standing position. Self-selected gait speed and distance covered within 6 min were determined before and after training to evaluate the impact of training on gait performance. Associated changes in gait kinematics were assessed with a three-dimensional motion analysis system. Results showed an improvement of gait speed (0.26 vs 0.35 m s^-1) and distance (23 vs 37 m) after nine gait-like vibration training sessions (+34.6%; +60.9%). In addition, more bilateral hip extension and larger left hip range of motion improved hip-knee cyclograms. Gait-like vibration training improved gait abilities in a person with chronic incomplete SCI.

Supraspinal Control Predicts Locomotor Function and Forecasts Responsiveness to Training after Spinal Cord Injury

Restoration of walking ability is an area of great interest in the rehabilitation of persons with spinal cord injury. Because many cortical, subcortical, and spinal neural centers contribute to locomotor function, it is important that intervention strategies be designed to target neural elements at all levels of the neuraxis that are important for walking ability. While to date most strategies have focused on activation of spinal circuits, more recent studies are investigating the value of engaging supraspinal circuits. Despite the apparent potential of pharmacological, biological, and genetic approaches, as yet none has proved more effective than physical therapeutic rehabilitation strategies. By making optimal use of the potential of the nervous system to respond to training, strategies can be developed that meet the unique needs of each person. To complement the development of optimal training interventions, it is valuable to have the ability to predict future walking function based on early clinical presentation, and to forecast responsiveness to training. A number of clinical prediction rules and association models based on common clinical measures have been developed with the intent, respectively, to predict future walking function based on early clinical presentation, and to delineate characteristics associated with responsiveness to training. Further, a number of variables that are correlated with walking function have been identified. Not surprisingly, most of these prediction rules, association models, and correlated variables incorporate measures of volitional lower extremity strength, illustrating the important influence of supraspinal centers in the production of walking behavior in humans.